1. Field of the Invention
The present invention relates to devices for supporting elongate tubular members and, more particularly, relates to an improved pipe shoe of the clamp-type for supporting lengths of insulated pipe during service above a pipe rack in an industrial or commercial facility.
2. Description of the Background
Commercial and industrial facilities, such as petrochemical plants, frequently support their process piping on a series of inverted U-shaped overhead racks each having a generally horizontal planar top surface. A dozen or more generally parallel pipes are typically supported at 6 to 12 inch spacings on the pipe racks, and carry gas or liquids throughout the facility. It is generally preferred that the process piping not rest directly on each pipe rack, and pipe shoes are thus commonly used to support each pipe a desired distance above the top surface of each pipe rack. Since the process piping is supported above the planar surface of the pipe rack, the piping may be initially installed on the pipe shoes, and the pipe thereafter wrapped or covered with an insulation to (a) retain heat within the fluid passing through the process piping, or (b) minimize the likelihood that liquids in the process piping will freeze during cold weather. Pipe shoes thus enable process piping to be insulated much more economically than if the piping had to be raised above the rack to install the insulation, then relowered onto the rack. Moreover, pipe shoes keep both the pipe and the insulation physically separated from the pipe rack, so that neither the pipe nor the insulation will be susceptible to deterioration. Such pipe shoes may be provided at, e.g. 20 foot intervals along the length of the process piping, and a single industrial petrochemical facility may utilize 100,000 pipe shoes or more to support its process piping on the pipe racks.
The prior art pipe shoes most commonly used include a base and a pair of axially spaced clamps for interconnecting the base to the pipe. The base comprises an inverted T-shaped member, so that the base can easily slide along the planar upper surface of the pipe rack as the process pipe thermally expands or contracts in length. A lower generally semi-circular clamp half is welded to each end of the base, so that the pipe "sits" in the lower clamp halves. An ear projects radially outward from each side of both the lower and upper clamp halves, so that the pipe may be fixedly connected to a base by placing the upper clamp half over the supported pipe, and interconnecting the mating radially-opposing ears of the upper and lower clamp halves with a pair of conventional bolts.
In spite of its widespread use, the above pipe shoe has significant disadvantages, particularly when used for supporting a pipe which will subsequently be insulated. Conventional pipe insulation typically is manufactured in axially split halves sized for a particular diameter pipe, so that the two insulation halves may be easily positioned about a pipe then taped or otherwise secured together to form an insulating sleeve of a desired thickness. Since the process pipe is supported by the pipe shoes along the rack, the insulation installer can quickly and reliably install this split insulation along the length of a given pipe between the shoes. The configuration of the shoes, however, presents a problem to the installer, particularly since the radially-opposing side ears project one inch or more outward from the pipe, and since the vertical bolts which interconnect the side ears are spaced significantly from the pipe. Accordingly, the installer typically cuts out a portion of the insulation where the clamp ears and bolts will be located, thereby allowing the sleeve-like insulation halves to be placed about the pipe and over the clamps. In many cases, the insulation installer must then "putty over" the cut out holes with a caulking material to reduce heat loss from the pipe. These operations take a significant amount of time, so that the cost of installing the insulation is directly related to the number of pipe shoes along the length of the process pipe.
Apart from the increased installation costs, the above described "repair" process does not adequately protect the pipe as well as the intended insulation does. The projecting ears on the clamp halves act as a heat sink, drawings valuable heat from the process pipe and releasing that heat to the atmosphere. The caulking tends to deteriorate, and in time cracks and breaks away from the projecting ears. Both the pipe and the insulation thus tend to deteriorate more quickly in the vicinity of the insulation cut outs, so that the useful life of the process line is decreased.
Another problem with prior art pipe shoes relating to deterioration concerns corrosion of the pipe and the shoe in the vicinity where the lowermost portion of the pipe engages the inner lowermost portion of the lower clamp half. Process piping frequently "sweats", so that relatively minor amounts of condensation on the outer surface of the pipe flow by gravity to the lowermost portion of the horizontal pipe. This sweating tends to present no serious problems, except at the locations of the pipe clamps. At these sites, the condensate encounters the area adjacent the adjoining lowermost arcuate surface of the pipe and the clamp, so that both the pipe and the clamp tend to corrode at these sites, thereby further decreasing the useful life of the process piping. This corrosion can be minimized by installing a plastic or other non-corrosive sheet between the inner surface of the lower clamp half and the pipe, although this additional operation again significantly increases the cost of installing the process pipe on the pipe rack.
A further disadvantage of prior art pipe shoes relates to the difficulty with running an electrical heating line or steam trace line along the insulated process piping to further reduce the likelihood of pipe breakage during cold weather. Such a heating line is often required to prevent the liquids in the pipe from freezing, but such lines are difficult to install when conventional pipe shoes are utilized. While the heating line can be run along the pipe and radially outside of the clamps when encountering a pipe shoe, this routing of the line decreases its efficiency. Moreover, this repeated routing of the heating lines around the pipe shoe clamps further increases installation costs, and leads to an increased number of points along the heating line which are susceptible to breakage, leakage, or other damage.
The disadvantages of the prior art are overcome by the present invention, and an improved pipe shoe and a method of installing a pipe shoe between a pipe and a pipe rack are hereinafter disclosed.